In newer gas turbine installation combustion chambers, weak premixing burners are employed which exhibit particularly low pollutant emissions when operated with gaseous fuels, such as natural gas or methane. Such a burner, designated a double-cone burner, is known from EP-B1 03 21 809. This double-cone burner for operating with either gaseous or liquid fuels has separate fuel lines for the two types of fuel. An atomizing nozzle is also necessary for the liquid fuel. Because it is designed for both types of fuel, the double-cone burner is therefore of larger configuration and is equipped with more components than would be necessary for operation with only one type of fuel.
In the previously known methods and appliances for supplying fuel to a combustion chamber operated with liquid fuels, such as diesel oil or extra-light heating oil, the evaporation of the fuel and the mixing of fuel vapor and combustion air takes place within the burners or the combustion chamber. The evaporating fuel droplets lead to low temperatures on the droplet and in the vicinity of droplets. In addition, inhomogeneous temperature and concentration fields occur in the combustion space because of the evaporating fuel. A wide distribution, which is difficult to control, of the local combustion temperatures and air ratios therefore occurs in the combustion space and this cannot be prevented even with adjustment to average stoichiometry of the combustion pairs. Because, however, the formation of oxides of nitrogen takes place very rapidly at high temperatures and, in contrast, the decomposition reactions of oxides of nitrogen are very much slower, inhomogeneous temperature and concentration fields lead to an increased formation of oxides of nitrogen. Summarizing, it can therefore be stated that the combustion of liquid fuels often results in NO.sub.X figures that are not satisfactorily low because parts of the evaporation and mixing processes take place in parallel, both spatially and in time.
In order to correct this disadvantage, tubes of small diameter are fitted as separate oil evaporation elements in the exhaust gas path of an engine, as described in Forster, S.: "Umweltfreundlicher Oldampf-Motor (Environmentally-friendly oil vapor engine)", in "Berichte des Forschungszentrums Julich (Reports of the Julich Research Center)", No. 2564, ISSN 0366-0885, pp. 1-4. This solution, however, requires very large additions of water (in the range of between 2 and 5 kg of water per kg of oil) in order to prevent deposits on the inside walls of the tubes and therefore blockage of them. Because of the high level of water addition and the associated efficiency losses, however, it is not possible to use such evaporation elements for the combustion of liquid fuels in gas turbine installations.